Conventional window and door manufacture has commonly used vinyl, wood and metal components in forming structural members.
Vinyl materials have been used in forming envelopes, trim and seal components in window units. Such vinyl materials typically comprise a major proportion of a vinyl polymer with inorganic pigment, fillers, lubricants, etc. Extruded or injection molded thermoplastic materials have been used in window and door manufacture. Filled and unfilled flexible and rigid thermoplastic materials have been extruded or injection molded into useful seals, trim components, fasteners, and other wood window construction parts.
Wood has been milled into shaped structural components that with glass can be assembled to form double hung or casement units, etc. and door assemblies. Wood windows, while structurally strong, useful and well adapted for use in many residential and commercial installations can have problems under certain circumstances related to the deterioration of the wood components. Wood windows also suffer from cost problems related to the availability of suitable wood for construction. Clear wood products are slowly becoming more scarce and are becoming more expensive as demand increases.
Metal, typically aluminum components, are also often combined with glass and formed into single unit sliding windows. Metal windows are typically suffer from the drawback that they tend to lose substantial quantities of heat from interior spaces.
Thermoplastic polyvinyl chloride has been combined with wood members in manufacturing PERMASHIELD.RTM. brand windows manufactured by Andersen Corporation for many years. The technology disclosed in Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,885, have been utilized in the manufacture of the plastic coatings or envelopes on wooden or other structural members. Generally, the cladding or coating technology used in making PERMASHIELD.RTM. windows involves extruded or injection molding a thin polyvinyl chloride coating or envelope onto a shaped wooden structural member. Polyvinyl chloride thermoplastic polymer materials have been combined with wood and wood fiber to make extruded or injection molded materials generally. However, the polyvinyl chloride materials of the prior art do not possess adequate properties to permit extrusion of structural members that are a direct replacement for wood. The polyvinyl chloride materials of the prior art do not have thermal and structural properties similar to wood members. The polymeric composites of the prior art fail to have sufficient compressive strength, modulus, coefficient of thermal expansion, coefficient of elasticity, workability or the ability to retain fasteners equivalent to or superior to wooden members. Further, many prior art extruded or injection molded composites must be milled to form a final useful shape. One class of composite, a polyvinyl chloride and wood flour material, poses the added problem that wood dust, which can accumulate during manufacture, tends to be explosive at certain concentrations of wood flour in the air.
Accordingly, a substantial need exists for an improved structural member that can be made of a polymer and wood fiber composite. The composite can contain an intentional recycle of a byproduct stream if desired. The composite can be extruded or injection molded into a shape that is a direct substitute in terms of assembly properties and structural properties, for the equivalent milled shape in a wooden structural member. The structural member requires a coefficient of thermal expansion that approximates wood, a material that can be extruded or injection molded into a reproducible stable dimension and a useful cross-section, a low heat transmission rate, an improved resistance to insect attack and rot while in use and a hardness and rigidity that permits sawing, milling and fastening retention comparable to wood members. Further, window and door manufacturers have become significantly sensitive to by-product streams produced in their manufacturing activities. Substantial quantities of wood by-product materials, including wood trim pieces, sawdust, wood milling gnawings; recycled thermoplastic including recycled polyvinyl chloride and other streams have caused significant expense to window manufacturers in disposal. Commonly, these materials are either burned for their heat value and electrical power generation or are shipped to qualified landfills for disposals. Such streams contain substantial proportions of hot melt and solvent-based adhesives, thermoplastics such as polyvinyl chloride, paint, preservatives and other organic materials. Substantial need exists to find a productive environmentally compatible use for such streams to avoid returning the materials into the environment in a harmful form.